Answer:
1.0 mol/L MgCl₂
Step-by-step explanation:
The formula for osmotic pressure is
Π = icRT
The only difference between the two solutions is their i factor.
MgCl₂
MgCl₂ ⟶ Mg²⁺ + 2Cl⁻
I = 1 + 2 = 3
NaNO₃
NaNO₃ ⟶ Na⁺ + NO₃⁻
i = 1 +1 = 2
MgCl₂ has a greater i value, so its solution has the greater osmotic pressure.